Ok here is my findings.
Pulling a ten car train, 8 cars having the double spring 2 cars normal, the only slinky affect I encountered is on the cars with normal couplers. I did not have an issues running the train on curves, thru turnouts, up or down grade. The only slack action was between the knuckles which did not mimic the slinky affect.
Not saying this is the cure as other ideas might get the same results, but I am pleased with the results. Only time will tell. Works for me. I think this is the way I am going to proceed.
ED I am definitely staying away from hydraulics & grease. LOL
Bill you idea with the wire insert may work, but with my physical limitations I would have trouble with that. So that experiment is in your hands. One thought, with the double springs vs the wire , there is still some sort on cushion with the springs.
Thank you all for listening & your input. Without this forum I would have thought slinky action was normal & acceptable.